High precision frequency source

[terry michaels]

Hello list members:

I have had a high stability audio signal source on my bench for years, it
is possible for anyone to put a similar setup together at low cost and
effort.   I think many others would be interested in how to obtain this
equipment, so I'll tell you how to do it.

My audio source generates sine waves from one Hertz to 160 MHz in one Hertz
increments, frequency is set with 9 rotary dials in a decade arrangement on
the front panel.  I am using a PTS ( Programmed Test Sources) model 160
synthesized signal generator, which generates frequencies from 100 KHz to
160 MHz, but you can get an output in the audio range, down to 1 Hz, as
follows.  

This unit has an internal 10 MHz crystal controlled oscillator, with an
output available from a BNC connector on the back of the unit.  Get a
passive double balanced mixer, such as an ANZAC MD-108 or similar,
(available used for $5 to $20), connect the LO port on the mixer to the 10
MHz out, connect the RF port on the mixer to the front panel main output of
the PTS 160, and you get your audio output from the IF port of the mixer. 
It would be good idea to run the output from the mixer through a simple
passive low pass filter, as the mixer generates the sum of the inputs
(around 20 MHz), and the difference (audio range).   You set the PTS 160 
10 MHz dial to the "1" position, and then set your desired audio range
output using the lowest decade frequency dials, there is a dial for 1's of
Hz, 10's of Hz, 100'z of Hertz, etc.  Usually the PTS 160 will have a
remote programming capability, so it is also possible to control the
frequency setting remotely with a computer.  You can command any frequency
within the range of the instrument with microsecond switching speed.

The frequency accuracy of the audio range signals generated this way is
extremely accurate, better than one part in 10 million.   The best part is,
although the PTS 160 is a current product selling for around $6,000.00, you
can find them used for $50.00 to $200.00.  I bought mine from a friend, but
I have seen them sell on Ebay a number of times in that price range, I
think they sell so cheap because most people don't know what it is.  There
is a PTS 160 on Ebay currently, at 
http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=452116001.  PTS
makes their frequency synthesizers with or without various options, if you
buy one, make sure it has the following:  internal reference, and front
panel controls.

If anyone needs additional information on this, just let me know.

Terry Michaels